Kinematics and Dynamics

[Buela_Vigneswaran]

Kinematics and Dynamics

1. Kinematics in Robotics

Kinematics focuses on the motion of robots without considering the forces causing the motion. It is divided into two primary areas: forward kinematics and inverse kinematics.

a. Forward Kinematics (FK)

• Definition:
  • Determines the position and orientation of the robot's end-effector (e.g., a robotic arm’s hand) given the joint parameters (angles, distances).
• Process:
  • Use geometric or matrix-based methods (homogeneous transformation matrices) to compute the pose (position + orientation).
• Applications:
  • Simulating robot motion, path planning, and visualization.

b. Inverse Kinematics (IK)

• Definition:
  • Calculates the joint parameters required to achieve a desired position and orientation of the end-effector.
• Complexity:
  • Non-linear equations make IK computationally intensive.
  • Solutions may be non-unique or infeasible due to constraints.
• Techniques:
  • Analytical Methods: Algebraic manipulation.
  • Numerical Methods: Iterative algorithms (e.g., Newton-Raphson).

2. Types of Robotic Motion

• Linear Motion: Straight-line movement of the end-effector.
• Rotational Motion: Movement around a fixed axis or point.
• Combined Motion: A combination of linear and rotational movements.

3. Dynamics in Robotics

Dynamics deals with the forces and torques causing the robot's motion. It is essential for designing and controlling robots to ensure stability and precision.

a. Forward Dynamics

• Definition:
  • Computes the resulting motion (accelerations, velocities) of a robot based on applied forces and torques.
• Applications:
  • Simulating robot behavior under external forces (e.g., gravity, friction).

b. Inverse Dynamics

• Definition:
  • Calculates the required forces and torques to achieve a desired motion.
• Applications:
  • Robot control, trajectory optimization, and power estimation.

4. Kinematic Chains

• Open Kinematic Chain:
  • A series of rigid links connected by joints with one end fixed and the other free (e.g., robotic arms).
• Closed Kinematic Chain:
  • A loop is formed when the chain's end is connected back to the base (e.g., parallel manipulators).

5. Degrees of Freedom (DoF)

• Definition:
  • The number of independent motions a robot can perform.
• Calculation:
  • Determined by the number and type of joints (e.g., revolute, prismatic).
• Examples:
  • A 6-DoF robot arm can move in six independent directions: three translational (x, y, z) and three rotational (roll, pitch, yaw).

6. Robot Workspace

• Definition:
  • The volume of space a robot’s end-effector can reach.
• Types:
  • Cartesian Workspace: Defined by x, y, z coordinates.
  • Joint Workspace: Defined by joint angles or displacements.

7. Jacobian Matrix

• Definition:
  • A mathematical representation that relates joint velocities to end-effector velocities.
• Importance:
  • Used in velocity kinematics, force analysis, and singularity detection.

8. Singularity in Robotics

• Definition:
  • A configuration where the robot loses one or more degrees of freedom, causing issues with control and stability.
• Example:
  • A robotic arm reaching full extension where certain motions are no longer achievable.
• Solution:
  • Avoid singularities through proper trajectory planning and design.

9. Tools and Techniques for Kinematics and Dynamics Analysis

• Mathematical Methods:
  • Matrix Algebra, Differential Calculus, Linear Algebra.
• Simulation Software:
  • MATLAB, Simulink, ROS, and Gazebo.
• Applications:
  • Animation, trajectory design, and robot control.

10. Practical Applications of Kinematics and Dynamics

• Industrial Robotics:
  • Programming precise movements for assembly and welding.
• Medical Robotics:
  • Designing surgical robots for high precision and accuracy.
• Autonomous Vehicles:
  • Kinematic models for navigation and obstacle avoidance.
• Humanoid Robots:
  • Calculating human-like motions for walking, running, and interacting.